(CNN) -- Virginia's new attorney general, Democrat Mark Herring, will announce Thursday that he has concluded that the state's ban on same-sex marriage is unconstitutional and he'll no longer defend the law in federal lawsuits.

"Virginia Attorney General Mark Herring will be filing a brief with the federal court in Norfolk this morning notifying them of a change in Virginia's position in the case of Bostic v. Rainey, a challenge to Virginia's ban on same-sex marriage," Herring's spokesman Michael Kelly said in an email to CNN."

"After a thorough legal review of the matter, Attorney General Herring has concluded that Virginia's current ban is in violation of the U.S. constitution and he will not defend it. Instead, the Commonwealth will side with the plaintiffs in seeking to have the ban declared unconstitutional," added Kelly.

Multiple lawsuits in Virginia charge that the Old Dominion's ban violates the U.S. Constitution's equal protection and due process clauses.

Herring will further explain his move in a news conference on Thursday and will say "It's time for Virginia to be on the right side of the law, and the right side of history," a source close to Herring said.

Herring, a former state senator, stressed marriage equality as part of his campaign last year. His election, along with the victory of Democrat Terry McAuliffe as governor, marked a major shift in Virginia politics as they replaced conservatives in the executive branch. The former Virginia Attorney General, Ken Cuccinelli, who narrowly lost the gubernatorial election to McAuliffe, was a strong opponent of legalizing same-sex marriage.

On McAuliffe's first day as governor earlier this month, he issued an executive order prohibiting discrimination against gay state employees.

Thursday's announcement in Virginia, a crucial battleground state in national politics, comes after federal judges recently struck down similar bans in Utah and Oklahoma.

Fifty-seven percent of Virginians voted to approve the same-sex marriage ban in 2006. But recent polling in the commonwealth indicates that a slight majority now support same-sex marriage.

The story was first reported by the Washington Post

Herring's victory was razor thin. On Election Day he was in a virtual dead heat with Republican Mark Obenshain, another state senator. The race went to a recount, and was not concluded until six weeks after the November election, when Obenshain conceded.